PIC18F4550 TQFP Experiment | Breakout board

Submitted by RakeshRon on Mon, 07/17/2017 - 18:47

PIC18F4550 has been an interesting Microcontroller so far for all kinds of experiments and learning for me. Interestingly Thin Quad Flat package is very small in size then that of a regular 40 pin Dual inline package and thereby reducing the size of the circuit board and project significantly. Sure the cost of TQFP is comparatively higher than the regular DIP PIC18F4550, but I found it worth to give it a try. Specifications are almost same to that of a regular dual inline package, only with four additional pins. There are lot of breakout board already available to get things started, but I preferred to make one for me rather than buying one.

DIP’s are easily available, but for TQFP variant of PIC18F4550 I had to wait for 25 days after placing order before it could be delivered as the local suppliers didn’t had these. It is more of an industrial grade package.

Unlike the regular DIP, the PIC18F4550 TQFP package has 44 Pins. This was my first ever attempt to work with TQFP. Since I was fairly new to micro soldering and dealing with small spaces, I had to practice a few times on old broken circuitry off some old malfunctioning router circuit board.

Note: Please be cautious while etching PCB, as it deals with potentially harmful chemical and equipment, the process is prone to accident. Micro soldering involves working with various equipment in a close proximity hence use necessary protective gears.

Like all the boards, the first step to begin with was to lay out a PCB design on my PCB designer. Probably this was the easiest part so far.

But the real fun begins while carefully etching the board and later soldering the contacts.

The Plan is to make a custom breakout board with Jumper pins, and later adjusting the breakout schematics to all my future PCB boards. It would allow me to switch the microcontroller boards back and forth across my other projects. DIP’s are larger in size and there is always possibility of breaking few pins while switching across the 40 pin base on a frequent basis. But on my custom TQFP breakout board jumper pins are strong enough to deal with constant switching between my boards; on the event of damage, the pins can be replaced easily. Also TQFP occupies less space thereby making the projects smaller.

Etching a circuit board with such small space between the pins is challenging. I would highly recommend to stick with glossy paper (heat transfer paper) for printing the board instead of regular paper. The distance between the pins are so little that incase of errors, it is hard to make any corrections with marker.

After few hours of careful soldering, the result was below. Fortunately I was able to make it work in the first attempt. I usually cover up the exposed copper with solder lead to mitigate the effects of corrosion after few months, also it makes the board less ugly.

I agree, not one of the best job in etching and soldering, but I tried by best.

Board 2 – The test board

Now since the board 1 which bears the Microcontroller is ready, it is time to test if it is working the way it’s supposed to be and all the contacts on the microcontroller is precise, without any loose ends. To do so I would need another board which would let me run experiments. The new board’s would bear female ports in the exact alignment to that of the male pins of the previous designed PIC18f4550 TQFN board 1, this new board if design carefully in perfect alignment should enable me to burn by codes with Pickit2 programmer.